Adding Cypress for e2e testing (#85)

* using the higher-level react-testing-library, and regenerating snapshot - renders real DOM elements
* Basic e2e testing with Cypress, following the guide here: https://www.gatsbyjs.com/docs/how-to/testing/end-to-end-testing/ ; needed to install cypress-local to avoid jest-cypress collision
* Adding accessibility testing support and basic a11y tests
* adding failure logging
* Adding nightly test run
* Fix misc stuff from lighthouse (#81)
* Removing local-cypress, relying instead on a combination
of type reference and eslint-plugin-cypress;
adding cypress to jest ignore paths to avoid conflict -
`npm test` is now jest-only, use `npm run test:e2e` to run cypress tests
* updating comment to clarify timezone

client/cypress/support/index.js

@@ -0,0 +1,18 @@
+// ***********************************************************
+// This example support/index.js is processed and
+// loaded automatically before your test files.
+//
+// This is a great place to put global configuration and
+// behavior that modifies Cypress.
+//
+// You can change the location of this file or turn off
+// automatically serving support files with the
+// 'supportFile' configuration option.
+//
+// You can read more here:
+// https://on.cypress.io/configuration
+// ***********************************************************
+
+import './commands';
+import 'cypress-axe';
+import '@testing-library/cypress/add-commands';